Study Of Piston Re-manufacture Using Laser Cladding

As a key part of diesel engine,piston works in high temperature,high pressure and heavy load.In recent years,with the continuous development of diesel technology,its enhancement factor is increasing,which requires higher and higher requirements for piston strength.In the practical application,the piston often wears out,especially under the worst condition of the first air ring groove position;when the position worn out,high temperature and high pressure gas in the combustion chamber will leak into the body,not only reduces the combustion efficiency,increase oil consumption serious the pressure of the body will increase and the engine stops working.Under normal circumstances,when the piston ring groove is worn,it is valued scrapped or repaired according to its value.The way of repair is usually done by brush plating,plating or overlaying.With the increase of environmental pressure,electroplating technology will be canceled gradually.The overlaying technology will bring thermal stress to parts,the repair process is complex and the stability is poor.Laser cladding has attracted much attention in the field of green re-manufacturing because of its high density,clean process and no pollution.The contents and conclusions of this paper are as follows:(1)By analyzing the failure piston of a diesel engine,including dimension measurement,chemical analysis and metallographic examination,it is determined that the failure mode of the diesel engine piston is wear,and the failure reason is abrasive wear caused by dust and sand in the environment.(2)Take the same 42 CrMo sample as the piston material and use 3 kinds of self-melting alloy powder with 11 different components to make the cladding test.By observing the cladding layer and the micro-structure of the bonding layer,the surface of the cladding layer and the hardness of the bonding layer,the cladding powder suitable for the piston is determined to be Fe60.(3)According to the narrow and deep characteristics of the piston.A total of 2 rounds of 12 groups of experiments were carried out by selecting appropriate laser incident angle,laser power,powder feed rate,scanning speed and other technological parameters.The micro-hardness tester is used to detect the surface hardness and hardness gradient to see if it meets the requirements of the original hardness layer.A metallographic microscope was used to observe the surface structure,internal structure and the structure of the laser cladding layer,and the quality of the cladding was evaluated.The reliability of laser cladding was evaluated by using wet fluorescent magnetic powder detection machine to detect the cladding layer and the structure of the joint with the matrix.Finally,the optimal process parameters are determined.(4)A small batch of products was tried to verify the feasibility of the application of the project.16 pistons were tested by the steps of treatment before cladding,control of cladding process and machining after cladding.Through appearance inspection,magnetic particle flaw detection and three coordinate testing,13 pistons were found to meet the re-manufacturing requirements,and the effectiveness of the repair process was verified.The research shows that laser cladding technology can be used for batch re-manufacturing of pistons,and the re-manufactured products are reliable,economical,environmentally friendly.The research results provide technical support for re-manufacturing similar products,and have good engineering practical value.